fix(windows): redraw Flutter only when the captured WebView frame changed

flutter_inappwebview_windows/windows/custom_platform_view/graphics_context.h

@@ -5,6 +5,8 @@
 #include <windows.ui.composition.h>
 #include <winrt/Windows.Foundation.h>
 
+#include <mutex>
+
 #include "util/rohelper.h"
 
 namespace flutter_inappwebview_plugin
@@ -24,6 +26,10 @@ namespace flutter_inappwebview_plugin
     {
       return device_context_.get();
     }
+    // The immediate context is shared by every WebView of the plugin and is
+    // not thread-safe. Hold this while issuing a sequence of calls on it from
+    // a thread other than the one that created it (capture threads).
+    std::mutex& device_context_mutex() const { return device_context_mutex_; }
 
     winrt::com_ptr<ABI::Windows::UI::Composition::ICompositor> CreateCompositor();
 
@@ -50,5 +56,6 @@ namespace flutter_inappwebview_plugin
       device_winrt_;
     winrt::com_ptr<ID3D11Device> device_{ nullptr };
     winrt::com_ptr<ID3D11DeviceContext> device_context_{ nullptr };
+    mutable std::mutex device_context_mutex_;
   };
 }

flutter_inappwebview_windows/windows/custom_platform_view/texture_bridge.cc

@@ -128,7 +128,7 @@ namespace flutter_inappwebview_plugin
       if (SUCCEEDED(frame->get_Surface(frame_surface.put()))) {
         last_frame_ =
           TryGetDXGIInterfaceFromObject<ID3D11Texture2D>(frame_surface);
-        has_frame = !ShouldDropFrame();
+        has_frame = last_frame_ && !ShouldDropFrame() && AcceptFrame(last_frame_);
       }
     }
 
@@ -148,6 +148,11 @@ namespace flutter_inappwebview_plugin
     }
   }
 
+  bool TextureBridge::AcceptFrame(const winrt::com_ptr<ID3D11Texture2D>&)
+  {
+    return true;
+  }
+
   bool TextureBridge::ShouldDropFrame()
   {
     if (!frame_duration_.has_value()) {
@@ -186,4 +191,4 @@ namespace flutter_inappwebview_plugin
       last_frame_timestamp_.reset();
     }
   }
-}
+}

flutter_inappwebview_windows/windows/custom_platform_view/texture_bridge.h

@@ -69,6 +69,13 @@ namespace flutter_inappwebview_plugin
     EventRegistrationToken on_frame_arrived_token_ = {};
 
     virtual void StopInternal();
+    // Called under |mutex_| for every captured frame that survived the fps
+    // limit. Returning false skips the frame: Flutter is not notified and the
+    // frame is not drawn. The base bridge accepts everything; the GPU bridge
+    // rejects frames whose pixels equal the frame Flutter already shows, since
+    // Windows.Graphics.Capture delivers a frame on every compositor tick even
+    // when the captured visual has not changed.
+    virtual bool AcceptFrame(const winrt::com_ptr<ID3D11Texture2D>& frame);
     void OnFrameArrived();
     bool ShouldDropFrame();